(1) When the compression spring does work, the elastic potential energy of the spring EP=WF. When the spring completely pushes away the mass p, there are:

EP= 12mPv2，v=4m/s，

∵ elastic collision between p and q,

∴ Yes: mpv=mpv'+mQv0,

12 MPV 2 = 12 MPV’2+ 12 mqv 02，

According to the above two formulas: v0=v=4m/s, v'=0.

(2) The slider Q slides on the trolley and makes a uniform deceleration motion. What is the acceleration? aQ=μmQgmQ=μg= 1m/s2

The car starts to accelerate uniformly at zero initial speed, and the acceleration is AM = μ mqgm = 13m/S2.

When the trolley and the slider reach the same speed, they will not drop or drop. When the time to reach the same speed is t, there are:

V 0-aQt = amount

Solution, t=3s.

The length l of the trolley is: v0t- 12aQt2? 12aMt2=L

The solution is L=6m.

A:

(1) The initial velocity v0 of Q just sliding on the car is 4m/s. 。

(2) The length of the trolley should be at least 6m to ensure that the slider Q will not fall off.